High-frequency signal level detection apparatus and high-frequency signal receiver apparatus using the same

ABSTRACT

In a high-frequency signal level detection apparatus for detecting an inputted signal level of a high-frequency signal, an AGC circuit executes an AGC on an intermediate frequency (IF) signal obtained by converting a frequency of a received high-frequency signal, using an RFAGC value and an IFAGC value for controlling gains of the high-frequency signal and the IF signal, respectively, based on the IF signal so that an output level of the IF signal is substantially constant. A controller previously measures first and second relational data, indicating an RFAGC value and an IFAGC value relative to the inputted signal level of the received high-frequency signal, respectively, measures the RFAGC and IFAGC values when a high-frequency signal to be measured is received, and detects the inputted signal level of the received high-frequency signal using the measured first and second relational data based on the measured RFAGC and IFAGC values.

TECHNICAL FIELD

The present invention relates to a high-frequency signal level detectionapparatus for detecting a signal level of a high-frequency signal whichis received by either an antenna or a cable, and to a high-frequencysignal receiver apparatus using the same high-frequency signal leveldetection apparatus.

BACKGROUND ART

As a high-frequency signal level detection apparatus for detecting asignal level of a high-frequency signal received by an antenna or acable, various kinds of apparatuses have been conventionally proposed,examples of which are disclosed in the following prior art documents.

(1) Japanese patent application laid-open publication No. 2002-217763(hereinafter, referred to as a prior art document 1).

(2) Japanese patent application laid-open publication No. 9-199962(hereinafter, referred to as a prior art document 2).

(3) Japanese patent application laid-open publication No. 60-062246(hereinafter, referred to as a prior art document 3).

(4) Japanese utility model laid-open publication No. 62-093843(hereinafter, referred to as a prior art document 4).

In each of these prior art documents 1 to 4, the signal level isbasically detected based on an AGC (Automatic Gain Control) voltage thatis a control voltage outputted from an AGC circuit that controls thesignal level of a received high-frequency signal to be substantiallyconstant.

The apparatus described in, for example, the prior art document 1(hereinafter, referred to as a prior art apparatus) is characterized bygenerating a mapping function by correcting an AGC value by apredetermined value for a signal at a predetermined frequency or higherat which a change in the AGC value is greater according tocharacteristics of a high-frequency circuit block, storing the generatedmapping function in a memory, correcting an AGC voltage by apredetermined value when a reception frequency at which an input levelis displayed exceeds the predetermined frequency, and calculating adisplay level value of an inputted signal by the mapping function so asto reduce a display error in the display of the input level, and thisleads to that an error may be caused due to a difference in receptionfrequency.

DISCLOSURE OF THE INVENTION

However, the prior art apparatus stores mapping function data in thememory. Due to this, in order to realize the display of the signal levelwith higher accuracy, a frequency range is divided into narrow frequencyranges and the mapping function data are stored for respective narrowfrequency ranges, resulting in an increase in a memory capacity. Whenthe signal level is displayed with a predetermined memory capacity,there is caused such a problem that the accuracy is insufficiently low.

Furthermore, the prior art apparatus calculates the signal level basedonly on a relationship between the signal level and an RFAGC voltage. Asa result, there is caused such a problem that the accuracy fordisplaying the signal level is often deteriorated. Besides, when aninterference signal is present on an adjacent channel, there is causedsuch a problem that the RFAGC voltage is influenced by the interferencesignal, resulting in deterioration of the accuracy for displaying thesignal level.

The object of the present invention is therefore to provide ahigh-frequency signal level detection apparatus capable of solving theabove-stated problems and detecting a signal level of a high-frequencysignal with accuracy higher than that of the prior art, and ahigh-frequency signal receiver apparatus using the same.

According to one aspect view of the present invention, there is provideda high-frequency signal level detection apparatus which includes an AGCcircuit and detecting means. The AGC circuit executes an automatic gaincontrol on an intermediate frequency signal obtained by converting afrequency of a received high-frequency signal, using an RFAGC value forcontrolling a gain of the high-frequency signal and an IFAGC value forcontrolling a gain of the intermediate frequency signal based on theintermediate frequency signal so that an output level of theintermediate frequency signal is substantially constant. The detectingmeans previously measures first relational data indicating an RFAGCvalue relative to an inputted signal level of the receivedhigh-frequency signal and second relational data indicating an IFAGCvalue relative to the inputted signal level of the receivedhigh-frequency signal. When a high-frequency signal to be measured isreceived, the detecting means measures the RFAGC value and the IFAGCvalue and detects the inputted signal level of the receivedhigh-frequency signal using the measured first and second relationaldata based on the measured RFAGC value and IFAGC value.

In the above-mentioned high-frequency signal level detection apparatus,the detecting means preferably detects the inputted signal level of thereceived high-frequency signal using only the second relational databased on the measured IFAGC value when the gain of the high-frequencysignal is a maximum value thereof.

In the above-mentioned high-frequency signal level detection apparatus,the detecting means preferably detects the inputted signal level of thereceived high-frequency signal using only the first relational databased on the measured RFAGC value when the gain of the high-frequencysignal is not a maximum value thereof.

In the above-mentioned high-frequency signal level detection apparatus,the detecting means preferably detects a first inputted signal level ofthe received high-frequency signal using the measured first relationaldata based on the measured RFAGC value, then detects a second inputtedsignal level of the received high-frequency signal using the measuredsecond relational data based on the measured IFAGC value, and thendetects an average value of the detected first and second inputtedsignal levels as the inputted signal level of the receivedhigh-frequency signal.

In the above-mentioned high-frequency signal level detection apparatus,the received high-frequency signal preferably has a plurality offrequencies. The detecting means preferably previously measures a firstrelational data indicating the RFAGC value relative to the inputtedsignal level and a second relational data indicating the IFAGC valuerelative to the inputted signal level using a high-frequency signalhaving a substantial central frequency among the frequencies.

In the above-mentioned high-frequency signal level detection apparatus,the received high-frequency signal preferably has a plurality offrequencies. The detecting means preferably previously measures thefollowing parts using two high-frequency signals having a maximumfrequency and a minimum frequency among the frequencies, respectively:

(a) a first part of the first relational data indicating the RFAGC valuerelative to the inputted signal level of the high-frequency signalhaving the maximum frequency;

(b) a first part of the second relational data indicating the IFAGCvalue relative to the inputted signal level of the high-frequency signalhaving the maximum frequency;

(c) a second part of the first relational data indicating the RFAGCvalue relative to the inputted signal level of the high-frequency signalhaving the minimum frequency; and

(d) a second part of the second relational data indicating the IFAGCvalue relative to the inputted signal level of the high-frequency signalhaving the minimum frequency.

After that, detecting means detects a first inputted signal level of thereceived high-frequency signal using the measured first part of thefirst relational data based on the measured RFAGC value, then detects asecond inputted signal level of the received high-frequency signal usingthe measured first part of the second relational data based on themeasured IFAGC value, and then detects an average value of the detectedfirst and second inputted signal levels as the inputted signal level ofthe high-frequency signal having the maximum frequency.

Further, detecting means detects a third inputted signal level of thereceived high-frequency signal using the measured second part of thefirst relational data based on the measured RFAGC value, then detects afourth inputted signal level of the received high-frequency signal usingthe measured second part of the second relational data based on themeasured IFAGC value, and then detects an average value of the detectedthird inputted signal level and the detected fourth inputted signallevel as the inputted signal level of the high-frequency signal havingthe minimum frequency.

Still further, detecting means calculates the inputted signal level ofthe high-frequency signal to be measured using a linear approximationmethod for linearly approximating the inputted signal level relative toa reception frequency of the high-frequency signal to be measured basedon the detected inputted signal level of the high-frequency signalhaving the maximum frequency and on the detected inputted signal levelof the high-frequency signal having the minimum frequency.

In the above-mentioned high-frequency signal level detection apparatus,the received high-frequency signal preferably has a plurality offrequencies, and a frequency range including the frequencies is dividedinto a plurality of frequency ranges. The detecting means preferablypreviously measures the first and second relational data in each of thedivided frequency ranges, and then detects the inputted signal level ofthe received high-frequency signal using the measured first and secondrelational data corresponding to the frequency range to which thefrequency of the high-frequency signal to be measured belongs.

In the above-mentioned high-frequency signal level detection apparatus,the detecting means preferably previously measures third relationaldata, that is a detected error in the IFAGC value of the secondrelational data indicating the IFAGC value relative to the inputtedsignal level of the received high-frequency signal, the detected errorbeing caused, between a case with an interference signal of a furtherhigh-frequency signal in the vicinity of the frequency of thehigh-frequency signal to be measured, and a case with no interferencesignal thereof. The detecting means preferably detects the detectederror using the third relational data based on the IFAGC value measuredfor the high-frequency signal to be measured, and corrects the detectedinputted signal level using the, detected error.

In the above-mentioned high-frequency signal level detection apparatus,the detecting means preferably previously measures the following parts:

(a) a first part of third relational data, that is a first detectederror in the IFAGC value of the second relational data indicating theIFAGC value relative to the inputted signal level of the receivedhigh-frequency signal, the first detected error being caused, between afirst case with interference signals of further high-frequency signalslocated on both sides of the frequency of the high-frequency signal tobe measured, and a case with no interference signal thereof; and

(b) a second part of the third relational data, that is a seconddetected error in the IFAGC value of the second relational dataindicating the IFAGC value relative to the inputted signal level of thereceived high-frequency signal, the second detected error being caused,between a second case with an interference signal of furtherhigh-frequency signal located on one side of the frequency of thehigh-frequency signal to be measured, and a case with no interferencesignal thereof.

The detecting means preferably detects one of the first and seconddetected errors based on the IFAGC value measured for the high-frequencysignal to be measured using one of the first and second parts of thethird relational data which respectively correspond to states in whichthe high-frequency signal to be measured is in the first and secondcases, and corrects the detected inputted signal level using thedetected error.

In the above-mentioned high-frequency signal level detection apparatus,the detecting means preferably represents the first relational data andthe second relational data by predetermined approximate functions,respectively, and detects the inputted signal level of the receivedhigh-frequency signal using the approximate function of the firstrelational data and the approximate function of the second relationaldata.

The above-mentioned high-frequency signal level detection apparatuspreferably further includes display means for displaying the inputtedsignal level detected by the detecting means.

According to another aspect view of the present invention, there isprovided a high-frequency signal receiver apparatus which includes areceiver for receiving a high-frequency signal, for converting thereceived high-frequency signal into an intermediate frequency signal,and for outputting the intermediate frequency signal and theabove-mentioned high-frequency signal level detection apparatus.

Therefore, according to the present invention, the first relational dataindicating the RFAGC value relative to the inputted signal level of thereceived high-frequency signal and the second relational data indicatingthe IFAGC value relative to the inputted signal level of the receivedhigh-frequency signal are measured in advance. The RFAGC value and theIFAGC value when the high-frequency signal to be measured is receivedare measured. Based on the measured RFAGC value and IFAGC value, theinputted signal level of the received high-frequency signal is detectedusing the measured first and second relational data. Therefore, it ispossible to detect the signal level of the high-frequency signal withaccuracy higher than that of the prior art.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a configuration of a televisionreceiver 100 that includes a high-frequency signal level detection anddisplay function according to a first preferred embodiment of thepresent invention.

FIG. 2 is a block diagram showing a configuration of a measurementcontrol system for generating a display control program for thehigh-frequency signal level detection and display function of thetelevision receiver 100 shown in FIG. 1.

FIG. 3 is a figure showing one example of a channel allocation of cabletelevision broadcasting signals in the U.S.A.

FIG. 4 is a flowchart showing a processing for generating the displaycontrol program, which is executed by a controller 60 of the measurementcontrol system shown in FIG. 2.

FIG. 5 is a flowchart showing a processing for controlling display,which is executed by a controller 50 shown in FIG. 1.

FIG. 6 is a graph showing an example of measurement results of an RFAGCregister value and an IFAGC register value relative to an inputtedsignal level in the television receiver 100 shown in FIG. 1.

FIG. 7 is a graph showing an approximate function obtained byapproximating measurement results of a relationship of the inputtedsignal level to the RFAGC register value shown in FIG. 6 by using apredetermined approximate function.

FIG. 8 is a graph showing an approximate function obtained byapproximating measurement results of a relationship of the inputtedsignal level to the IFAGC register value shown in FIG. 6 by using apredetermined approximate function.

FIG. 9 is a figure showing frequency ranges FR1 and FR2 that areobtained by dividing a frequency range of a broadcasting signal into tworanges and used in a television receiver 100 according to a secondpreferred embodiment of the present invention.

FIG. 10 is a flowchart showing a processing for generating a displaycontrol program, which is executed by a controller 60 of a measurementcontrol system according to the second preferred embodiment.

FIG. 11 is a flowchart showing a processing for controlling display,which is executed by a controller 50 according to the second preferredembodiment.

FIG. 12 is a figure showing minimum frequencies f_(1min) and f_(2min),maximum frequencies f_(1max) and f_(2max) in respective frequency rangesFR1 and FR2 obtained by dividing a frequency range into two ranges, anda reception frequency f_(rec), which are used in a television receiver100 according to a third preferred embodiment of the present invention.

FIG. 13 is a flowchart showing a first part of a processing forgenerating a display control program, which is executed by a controller60 of a measurement control system according to the third preferredembodiment.

FIG. 14 is a flowchart showing a second part of a processing forgenerating a display control program, which is executed by a controller60 of a measurement control system according to the third preferredembodiment.

FIG. 15 is a flowchart showing a processing for controlling display,which is executed by a controller 50 according to the third preferredembodiment.

FIG. 16 is a flowchart showing a processing for generating a displaycontrol program, which is executed by a controller 60 of a measurementcontrol system according to a fourth preferred embodiment.

FIG. 17 is a flowchart showing a processing for controlling display,which is executed by a controller 50 according to the fourth preferredembodiment.

FIG. 18 is a graph showing an approximate function AF52 obtained byapproximating measurement results of a relationship of an inputtedsignal level equal to or larger than a predetermined threshold value toan RFAGC register value by using a predetermined approximate function.

FIG. 19 is a graph showing an approximate function AF51 obtained byapproximating measurement results of a relationship of the inputtedsignal level equal to or smaller than the predetermined threshold valueto an IFAGC register value by using a predetermined approximatefunction.

FIG. 20 is a flowchart showing a first part of a processing forgenerating a display control program, which is executed by a controller60 of a measurement control system according to a fifth preferredembodiment.

FIG. 21 is a flowchart showing a second part of a processing forgenerating a display control program, which is executed by a controller60 of a measurement control system according to a fifth preferredembodiment.

FIG. 22 is a flowchart showing a processing for controlling display,which is executed by a controller 50 according to the fifth preferredembodiment.

FIG. 23 is a flowchart showing a first part of a processing forgenerating a display control program, which is executed by a controller60 of a measurement control system according to a sixth preferredembodiment.

FIG. 24 is a flowchart showing a second part of a processing forgenerating a display control program, which is executed by a controller60 of a measurement control system according to a sixth preferredembodiment.

FIG. 25 is a flowchart showing a processing for controlling display,which is executed by a controller 50 according to the sixth preferredembodiment.

FIG. 26 is a spectral view showing such a case that two interferencesignals on adjacent channels are present on both sides of a receptionchannel for a television receiver 100 according to a seventhpreferred-embodiment.

FIG. 27 is a graph showing IFAGC register values and RFAGC registervalues relative to inputted signal levels in three cases when theinterference signal on adjacent channel is not present, when oneinterference signal is present, and when two interference signals arepresent, respectively, in the television receiver 100 according to theseventh preferred embodiment.

FIG. 28 is a graph showing the IFAGC register value relative to a ratio(U/D) of an interference signal power to a desired wave power in thetelevision receiver 100 according to the seventh preferred embodiment.

FIG. 29 is a graph showing a display error ER2 of the inputted signallevel relative to the IFAGC register value in the television receiver100 according to the seventh preferred embodiment.

FIG. 30 is a flowchart showing a characteristic part of a processing forcontrolling display executed by a controller 50 according to the seventhpreferred embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Various kinds of referred preferred embodiments according to the presentinvention will be described below with reference to the drawings.Components similar to each other are denoted by the same numericalreferences.

First Preferred Embodiment

FIG. 1 is a block diagram showing a configuration of a televisionreceiver 100 that includes a high-frequency signal level detection anddisplay function according to a first preferred embodiment of thepresent invention FIG. 2 is a block diagram showing a configuration of ameasurement control system for generating a display control program forthe high-frequency signal level detection and display function of thetelevision receiver 100 shown in FIG. 1.

The television receiver 100 according to the present preferredembodiment is a high-frequency signal receiver apparatus that includes aset-top box (where a video signal processing is executed by a part up toan RGB switch 17 shown in FIG. 1, and an audio signal processing isexecuted by a part up to a low frequency amplifier 20 shown in FIG. 1)for receiving a digital broadcasting signal such as a cable television(hereinafter, referred to as a CATV). The television receiver 100includes an AGC circuit 30 that generates an RFAGC voltage forcontrolling an attenuation amount of an attenuator 4 so as to keep asignal level of a high-frequency (RF) signal substantially constant, andan IFAGC voltage for controlling an amplification factor of anintermediate frequency amplifier 7 so as to keep a signal level of anintermediate frequency (IF) signal substantially constant. In this case,as shown in FIG. 4, a controller 60 of the measurement control system ischaracterized by controlling a high-frequency signal generator 65 tochange an inputted signal level of a high-frequency signal inputted toan input terminal 1, calculating each of approximate functions AF1 andAF2 based on relationships of an IFAGC register value and an RFAGCregister value to the changed inputted signal levels, respectively,generating a display control program (FIG. 5) including theseapproximate functions AF1 and AF2, and writing the generated displaycontrol program into a program memory 51 of a controller 50. Further,the controller 50 of the television receiver 100 is characterized byexecuting the display control program shown in FIG. 5, so as tocalculate an inputted signal level Pif using the approximate functionAF1 based on the IFAGC register value and to calculate an inputtedsignal level Prf using the approximate function AF2 based on the RFAGCregister value, and to calculate and display an average value of theseinputted signal levels Pif and Prf as an inputted signal level Pin whena user actually views and listens to the broadcasting signal.

First of all, the configuration and operation of the television receiver100 shown in FIG. 1 will be described below in detail.

Referring to FIG. 1, a head end apparatus of a CATV broadcasting companyis connected to the input terminal 1 through, for example, a coaxialcable. A front end circuit 2 is configured to include a high-frequencyamplifier 3, the attenuator 4, the attenuation amount of which iscontrolled by the RFAGC voltage outputted from a low-pass filter (LPF)45 within the AGC circuit 30, the local oscillator 5, a localoscillation frequency of which is controlled by the controller 50, so asto control a frequency of a broadcasting channel from the televisionreceiver 100, and a mixer 6. The digital broadcasting signal from thehead end apparatus is inputted to the mixer 6 through the input terminal1, the high-frequency amplifier 3, and the attenuator 4. On the otherhand, a local oscillation signal from the local oscillator 5 is inputtedto the mixer 6. The mixer 6 mixes up the two inputted signals, andoutputs a resultant mixed signal to an A/D converter 10 through theintermediate frequency amplifier 7, an SAW bandpass filter 8, and anintermediate frequency amplifier 9. In this case, the SAW bandpassfilter 8 substantially band-passes only a signal component on onechannel of the broadcasting signal, so as to extracts a low frequencyconverted intermediate frequency signal (hereinafter, referred to as anIF signal) corresponding to the signal component on one channel of thebroadcasting signal, from the resultant mixed signal. Further, the A/Dconverter 10 converts the inputted IF signal into a digital signal at apredetermined sampling frequency, and outputs the digital signal to adigital demodulator 11 and an AGC detector circuit 31 that includes anRF-IF control function and that is provided in the AGC circuit 30.

The digital demodulator 11 includes an error correction circuit anddigitally demodulates the inputted digital signal and outputs thedemodulated signal to a TS decoder 12. The TS decoder 12 transmits theinputted digitally-demodulated digital signal to a descrambler 14through an POD card section 13 that stores security information on thebroadcasting company. Then the descrambler 14 descrambles thedigitally-demodulated digital signal, extracts a transport stream signal(hereinafter, referred to as a TS signal) from the descrambled digitalsignal, and outputs the extracted TS signal to an AV decoder 15. The AVdecoder 15 decodes a digital video signal and a digital audio signalfrom the inputted TS signal, outputs the digital video signal to an RGBprocessor 16, and outputs the digital audio signal to the low frequencyamplifier 20. The RGB processor 16 converts the inputted digital videosignal into an RGB video signal, and outputs the RGB video signal to aliquid crystal display 18 through the RGB switch 17. In this case, theRGB switch 17 superimposes an RGB signal generated by an OSD (On ScreenDisplay) controller 19 based on data of the inputted signal level of thebroadcasting signal from the controller 50, on the RGB signal from theRGB processor 16, and outputs a resultant superimposed RGB signal to theliquid crystal display 18 as will be described later in detail. Further,the low frequency amplifier 20 includes an A/D converter and convertsinputted two channels of digital audio signals into analog audiosignals, and outputs the analog audio signals to left and rightloudspeakers 22 and 21.

The AGC circuit 30 is configured to include the AGC detector circuit 31that includes the RF-IF control function, loop filters 32 and 42, anIFAGC register 33, an RFAGC register 433 pulse width modulators 34 and44, and low-pass filters 35 and 45. The AGC detector circuit 31 detectsthe IF signal inputted from the A/D converter 10, determines anoperating ratio of an RFAGC to an IFAGC from a level value of the IFsignal, generates an RFAGC signal and an IFAGC signal based on thedetermined ratio, and then, controls an RFAGC loop and an IFAGC loop, soas to adjust the broadcasting signal inputted at various kinds ofinputted signal levels depending on a reception location or a receptionchannel (e.g., at an inputted signal level difference of about 90 dBwhen the received broadcasting signal is a terrestrial digitalbroadcasting signal, and at an inputted signal level difference of about30 dB for a digital cable) to substantially such a constant amplitudelevel that the digital demodulator 11 in rear of the AGC detectorcircuit 31 can correctly demodulate the broadcasting signal. The IFAGCsignal from the AGC detector circuit 31 is subjected to time averagingby the loop filter 32 that serves as a predetermined low-pass filter,and a signal value of the resultant IFAGC signal is temporarily storedin the IFAGC register 33. Further, the pulse width modulator 34modulates a pulse width of the IFAGC signal according to an IFAGCregister value stored in the IFAGC register 33 using, for example, Δ-Σmodulation method, and the pulse width modulated IFAGC signal istransformed to the IFAGC voltage through the bandpass filter 35, and theIFAGC voltage becomes a control signal for controlling the amplificationfactor of the intermediate frequency amplifier 7. On the other hand, theRFAGC signal from the AGC detector circuit 31 is subjected to timeaveraging by the loop filter 42 that serves as a predetermined low-passfilter, and a signal value of the resultant RFAGC signal is temporarilystored in the RFAGC register 43. Further, the pulse width modulator 44modulates a pulse width of the RFAGC signal according to an RFAGCregister value stored in the RFAGC register 43 using, for example, theΔ-Σ modulation method, and the pulse width modulated RFAGC signal istransformed to the RFAGC voltage through the bandpass filter 45, and theRFAGC voltage becomes a control signal for controlling the attenuationamount of the attenuator 4.

In this case, the IFAGC register value and the RFAGCA register valuestored in the IFAGC register 33 and the RFAGC register 43, respectively,are read out by the controller 50, and used to generate the approximatefunctions AF1 and AF2, to be described later in detail, as well as tocalculate the inputted signal level Pin.

The controller 50, which is constituted by, for example, amicrocomputer, controls entirety of the television receiver 100according to a program stored in the program memory. 51, and stores datathat is temporarily calculated during execution of the program in thedata memory 52. An input unit 53 for inputting a channel number forselecting a broadcasting channel, a command to display the inputtedsignal level and the like is connected to the controller 50. Inaddition, the liquid crystal display 54 for displaying input values andset values inputted or set to the controller 50 is connected to thecontroller 50. In the present preferred embodiment, the controller 50executes the display control program generated by the controller 60shown in FIG. 2 and stored in the program memory 51, so as to calculateand display the inputted signal level of the digital broadcasting signalwhich the user views and listens to.

In the measurement control system shown in FIG. 2, a high-frequencysignal generator 65 is connected to the input terminal 1 of thetelevision receiver 100, and the controller 60 controls a frequency of ahigh-frequency signal generated -by the high-frequency signal generator65. The controller 60, which is constituted by, for example, amicrocomputer, controls entirety of the measurement control systemaccording to a program stored in a program memory 61, and stores datathat is temporarily calculated during execution of the program in a datamemory 62. An input unit 63 for inputting a command to generate adisplay control program and the like is connected to the controller 60.In addition, a liquid crystal display 64 for displaying input values andset values inputted or set to the controller 60 and an operating stateis connected to the controller 60. In the present preferred embodiment,the controller 60 executes the processing for generating the displaycontrol program shown in FIG. 4 stored in the program memory 61 as willbe described later in detail. Then the controller 60 controls thehigh-frequency signal generator 65 to change the inputted signal levelof the high-frequency signal inputted to the input terminal 1,calculates the approximate functions AF1 and AF2 based on therelationships of IFAGC register values and RFAGC register values to thechanged inputted signal levels, respectively, generates the displaycontrol program (FIG. 5) including these approximate functions AF1 andAF2, and writes the generated display control program into the programmemory 51 of the controller 50.

FIG. 3 is a figure showing one example of a channel allocation of CATVbroadcasting signals in the US. As apparent from FIG. 3, the channels ofthe CATV broadcasting signals in the US include broadcasting signalsfrom a 57-MHz broadcasting signal on Channel 2 to an 861-MHzbroadcasting signal on Channel 135 through a 459-MHz broadcasting signalon Channel 63.

FIG. 4 is a flowchart showing a processing for generating the displaycontrol program, which is executed by the controller 60 of themeasurement control system shown in FIG. 2.

Referring to FIG. 4, at step S1, with controlling the high-frequencysignal generator 65 to change the inputted signal level of thehigh-frequency signal inputted to the input terminal 1 and having ageneral central frequency of, for example, 459 MHz from −20 dBmV to +20dBmV every one dBmV, the controller 60 reads out IFAGC register valuesand RFAGC register values corresponding to respective inputted signallevels from the IFAGC register 33 and the RFAGC register 43,respectively, and stores the read-out same values in the data memory 62.Next, at step S2, the controller 60 calculates the approximate functionAF1 of the relationship of the IFAGC register values to the respectiveinputted signal levels based on the data representing the relationship.At step S3, the controller 60 calculates the approximate function AF2 ofthe relationship of the RFAGC register values to the respective inputtedsignal levels based on the data representing the relationship. Further,at step S4, the controller 60 generates the display control program(FIG. 5) including the calculated approximate functions AF1 and AF2, andwrites the generated program in the program memory 51 of the controller50, thus finishing the processing for generating the display controlprogram. In this case, each of the approximate functions can becalculated in a form of, for example, a cubic equation such asy=ax³+bx²+cx+d using a numerical calculation method such as a leastsquare method. In subsequent preferred embodiments, forms andcalculation methods of approximate functions are similar to thoseaccording to the present invention.

FIG. 5 is a flowchart showing a processing for controlling display,which is executed by the controller 50 shown in FIG. 1.

Referring to FIG. 5, at step S11, the controller 50 judges whether ornot a command to display the inputted signal level is inputted from theinput unit 53. If YES at step S11, the processing flow goes to step S12.If NO at step S11, the processing flow returns to step S11. Then, atstep S12, the controller 50 reads out the IFAGC register value from theIFAGC register 33 and reads out the RFAGC register value from the RFAGCregister value 43. At step S13, the controller 50 calculates theinputted signal level Pif using the approximate function AF1 based onthe read-out IFAGC register value. At step S14, the controller 50calculates the inputted signal level Prf using the approximate functionAF2 based on the read-out RFAGC register value. Further, at step S15,the controller 50 calculates an average value of the calculated inputtedsignal levels Pif and Prf as the inputted signal level Pin using thefollowing equation (1) based on the calculated inputted signal levelsPif and Prf:Pin=(Pif+Prf)/2  (1).

Further, at step S16, the controller 50 generates display data fordisplaying the calculated inputted signal level Pin, and outputs thegenerated display data to the OSD controller 19. The processing flowthen returns to step S11.

FIG. 6 is a graph showing an example of measurement results of the RFAGCregister value and the IFAGC register value relative to the inputtedsignal level in the television receiver 100 shown in FIG. 1. As apparentfrom FIG. 6, there is such a characteristic that, with increasing of theinputted signal level, the RFAGC register value is substantiallyconstant relative to the inputted signal level of up to about −6 dBmV atwhich level the attenuation amount of the attenuator 4 becomes theminimum and an RF gain is set to the maximum thereof, and graduallydecreases relative to the inputted signal level of greater than about −6dBmV. On the other hand, there is such a characteristic that, withincreasing of the inputted signal level, the IFAGC register valuegradually decreases relative to the inputted signal level of up to about−6 dBmV, and being constant relative to the inputted signal level ofgreater than about −6 dBmV.

FIG. 7 is a graph showing an approximate function AF2 obtained byapproximating the measurement results of the relationship of theinputted signal level to the RFAGC register value shown in FIG. 6 byusing a predetermined approximate function. As apparent from FIG. 7,although there is a slight error between the measured values and theapproximate function AF2 in a range of the inputted signal level from −5dBmV to −10 dBmV, the obtained approximate function AF2 generallycoincides with the measured values in the other range.

FIG. 8 is a graph showing an approximate function AF1 obtained byapproximating the measurement results of the relationship of theinputted signal level to the IFAGC register value shown in FIG. 6 byusing a predetermined approximate function. As apparent from FIG. 8,although there is a slight error between the measured values and theapproximate function AF1 in a range of the inputted signal level from−10 dBmV to −0 dBmV, the obtained approximate function AF1 generallycoincides with the measured values in the other range.

As described so far, in the processing for controlling display shown inFIG. 5 according to the first preferred embodiment, when the user viewsand listens to the digital broadcasting signal, the inputted signallevel Pif is calculated using the approximate function AF1 based on theIFAGC register value, the inputted signal level Prf is calculated usingthe approximate function AF2 based on the RFAGC register value, and theaverage value of the inputted signal levels Pif and Prf is calculatedand displayed as the inputted signal level Pin. Therefore, it ispossible to average the errors shown in FIGS. 7 and 8 described above,and detect and display the inputted signal level of the receivedbroadcasting signal with accuracy higher than that of the prior art.

Second Preferred Embodiment

FIG. 9 is a figure showing frequency ranges FR1 and FR2 that areobtained by dividing a frequency range of a broadcasting signal into tworanges and used in a television receiver 100 according to a secondpreferred embodiment of the present invention. The second preferredembodiment is characterized as follows. If an inputted signal level of adigital broadcasting signal is to be detected, attention is paid to afact that the characteristic shown in FIG. 6 is changed according to thefrequency of the broadcasting signal, and a frequency range includingall channels of CATV broadcasting signals is divided into two ranges,i.e., a first frequency range FR1 and a second frequency range FR2 asshown in FIG. 9. An approximate function AF11 representing arelationship between the inputted signal level and an IFAGC registervalue and an approximate function AF12 representing a relationshipbetween the inputted signal level and an RFAGC register value at ageneral central frequency f_(1c) in the first frequency range FR1, andan approximate function AF21 representing a relationship between theinputted signal level and the IFAGC register value and an approximatefunction AF22 representing a relationship between the inputted signallevel and the RFAGC register value at a general central frequency f_(2c)in the second frequency range FR2 are calculated. Inputted signal levelsPif and Prf are calculated using the two approximate functions of acorresponding frequency range in which a channel that user views andlistens to is included. Thereafter, similarly to the first preferredembodiment, these inputted signal levels Pif and Prf are averaged tocalculate an inputted signal level Pin.

FIG. 10 is a flowchart showing a processing for generating a displaycontrol program, which is executed by a controller 60 of a measurementcontrol system according to the second preferred embodiment.

Referring to FIG. 10, at step S21, with controlling a high-frequencysignal generator 65 to change the inputted signal level of thehigh-frequency signal inputted to an input terminal 1 and having thegeneral central frequency f_(1c) of 255 MHz within the first frequencyrange FR1 from −20 dBmV to +20 dBmV every one dBmV, the controller 60reads out IFAGC register values and RFAGC register values correspondingto the respective inputted signal levels from an IFAGC register 33 andan RFAGC register 43, respectively, and stores the read-out same valuesin a data memory 62. Next, at step S22, with controlling thehigh-frequency signal generator 65 to change the inputted signal levelof the high-frequency signal inputted to the input terminal 1 and havingthe general central frequency f_(2c) of 663 MHz within the secondfrequency range FR2 from −20 dBmV to +20 dBmV every one dBmV, thecontroller 60 reads out IFAGC register values and RFAGC register valuescorresponding to the respective inputted signal levels from the IFAGCregister 33 and the RFAGC register 43, respectively, and stores theread-out same values in the data memory 62. Then, at step S23, thecontroller 60 calculates the approximate function AF11 of therelationship of the IFAGC register values to the respective inputtedsignal levels within the first frequency range FR1 based on the datarepresenting the relationship. At step S24, the controller 60 calculatesthe approximate function AF12 of the relationship of the RFAGC registervalues to the respective inputted signal levels within the firstfrequency range FR1 based on the data representing the relationship.Further, at step S25, the controller 60 calculates the approximatefunction AF21 of the relationship of the IFAGC register values to therespective inputted signal levels within the second frequency range FR2based on the data representing the relationship. At step S26, thecontroller 60 calculates the approximate function AF22 of therelationship of the RFAGC register values to the respective inputtedsignal levels within the second frequency range FR2 based on the datarepresenting the relationship. Further, at step S27, the controller 60generates a display control program (FIG. 11) including the calculatedapproximate functions AF11, AF12, AF21, and AF22, and writes thegenerated display control program into the program memory 51 of thecontroller 50, thus finishing the processing for generating the displaycontrol program.

FIG. 11 is a flowchart showing a processing for controlling display,which is executed by a controller 50 according to the second preferredembodiment.

Referring to FIG. 11, at step S31, the controller 50 judges whether ornot a command to display the inputted signal level is inputted from aninput unit 53. If YES at step S31, the processing flow goes to step S32.If NO at step S31, the processing flow returns to step S31. At step S32,the controller 50 reads out the IFAGC register value from the IFAGCregister 33 and reads out the RFAGC register value from the RFAGCregister value 43. Next, at step S33, the controller 50 judges whetheror not a current reception frequency f_(rec) is fallen within the firstfrequency range FR1. If YES at step S22, the processing flow goes tostep S34. If NO at step S22, the processing flow goes-to step S36. Atstep S34, the controller 50 calculates the inputted signal level Pifusing the approximate function AF11 based on the read-out IFAGC registervalue. At step S35, the controller 50 calculates the inputted signallevel Prf using the approximate function AF12 based on the read-outRFAGC register value, and the processing flow goes to step S38. On theother hand, at step S36, the controller 50 calculates the inputtedsignal level Pif using the approximate function AF21 based on theread-out IFAGC register value. At step S37, the controller 50 calculatesthe inputted signal level Prf using the approximate function AF22 basedon the read-out RFAGC register value, and the processing flow goes tostep S38. Further, at step S38, the controller 50 calculates an averagevalue of the calculated inputted signal levels Pif and Prf as theinputted signal level Pin using the equation (1) based on the calculatedinputted signal levels Pif and Prf. At step S39, the controller 50generates display data for displaying the calculated inputted signallevel Pin, and outputs the generated display data to an OSD controller19. The processing flow then returns to step S31.

As described so far, in the processing for controlling display shown inFIG. 11 according to the second preferred embodiment, when the userviews and listens to the digital broadcasting signal, the inputtedsignal level Pif is calculated using the approximate function AF11 orAF21 corresponding to the frequency range FR1 or FR2 included in thefrequency of the viewed digital broadcasting signal based on the IFAGCregister value, the inputted signal level Prf is calculated using theapproximate function AF12 or AF22 corresponding to the frequency rangeFR1 or FR2 included in the frequency of the viewed digital broadcastingsignal based on the RFAGC register value, and the average value of theinputted signal levels Pif and Prf is calculated and displayed as theinputted signal level Pin. Therefore, it is possible to average theerrors shown in FIGS. 7 and 8 described above, substantially eliminatethe error due to the change in the frequency of the broadcasting signal,and detect and display the inputted signal level of the receivedbroadcasting signal with accuracy higher than that of the prior art.

In the preferred embodiment stated above, the frequency range of thebroadcasting signal is divided into the two frequency ranges FR1 andFR2. Alternatively, the frequency range may be divided into three ormore frequency ranges and approximate functions may be calculated. Thesame thing is true for the subsequent preferred embodiments.

Third Preferred Embodiment

FIG. 12 is a figure showing minimum frequencies f_(1min) and f_(2min),maximum frequencies f_(1max) and f_(2max) in respective frequency rangesFR1 and FR2 obtained by dividing a frequency range into two ranges, anda reception frequency f_(rec), which are used in a television receiver100 according to a third preferred embodiment of the present invention.The third preferred embodiment is characterized as follows. If aninputted signal level of a digital broadcasting signal is to bedetected, attention is paid to a fact that the characteristic shown inFIG. 6 is changed according to a frequency of the broadcasting signal,and the frequency range of all channels of CATV broadcasting signals isdivided into the two ranges, i.e., the first frequency range FR1 and thesecond frequency range FR2 as shown in FIG. 12. In addition, thefollowing approximate functions are calculated.

(a) An approximate function AF31 a representing a relationship betweenthe inputted signal level and an IFAGC register value and an approximatefunction AF31 b representing a relationship between the inputted signallevel and an RFAGC register value at the minimum frequency f_(1min) inthe first frequency range FR1.

(b) An approximate function AF32 a=AF41 a representing a relationshipbetween the inputted signal level and the IFAGC register value and anapproximate function AF32 b=AF41 b representing a relationship betweenthe inputted signal level and the RFAGC register value at each of themaximum frequency f_(1max) in the first frequency range FR1 and theminimum frequency f_(2min) the second frequency range FR2.

(c) An approximate function AF42 a representing a relationship betweenthe inputted signal level and the IFAGC register value and anapproximate function AF42 b representing a relationship between theinputted signal level and the RFAGC register value at the maximumfrequency f_(2max) in the second frequency range FR2.

Further, at each of the minimum frequency and the maximum frequency of afrequency range in which a channel that user views and listens to isincluded, inputted signal levels Pif and Prf are calculated using thetwo corresponding approximate-functions, and similarly to the firstpreferred embodiment, these inputted signal levels Pif and Prf areaveraged to calculate average values P_(fmin) and P_(fmax) of theinputted signal levels at the minimum frequency and the maximumfrequency in this frequency range, respectively. Further, based on thecalculated inputted signal level average values P_(fmin) and P_(fmax),an inputted signal level Pin is calculated using the following equation(2) by a linear approximation method for linearly approximating theinputted signal level relative to a reception frequency on assumptionthat the inputted signal level is linearly changed relative to afrequency between the minimum frequency and the maximum frequency in apredetermined frequency range:

$\begin{matrix}{{Pin} = {{\frac{f_{rec} - f_{nmin}}{f_{nmax} - f_{nmin}} \times P_{f\;{ma}\; x}} + {\frac{f_{nmax} - f_{rec}}{f_{nmax} - f_{nmin}} \times {P_{fmin}.}}}} & (2)\end{matrix}$

In this case, f_(rec) denotes a reception frequency, n is one in thefirst frequency range FR1 and two in the second frequency range FR2.

FIGS. 13 and 14 are flowcharts showing a processing for generating adisplay control program, which is executed by a controller 60 of ameasurement control system according to the third preferred embodiment.

Referring to FIG. 13, at step S41, with controlling a high-frequencysignal generator 65 to change the inputted signal level of thehigh-frequency signal inputted to an input terminal 1 and having theminimum frequency f_(1min) of 57 MHz within the first frequency rangeFR1 from −20 dBmV to +20 dBmV every one dBmV, the controller 60 readsout IFAGC register values and RFAGC register values corresponding to therespective inputted signal levels from an IFAGC register 33 and an RFAGCregister 43, respectively, and stores the read-out same values in a datamemory 62. Next, at step S42, with controlling the high-frequency signalgenerator 65 to change the inputted signal level of the high-frequencysignal inputted to the input terminal 1 and having the maximum frequencyf_(1max) of 459 MHz within the first frequency range FR1 and the minimumfrequency f_(2min) of 459 MHz within the second frequency range FR2 from−20 dBmV to +20 dBmV every one dBmV, the controller 60 reads out IFAGCregister values and RFAGC register values corresponding to therespective inputted signal levels from the IFAGC register 33 and theRFAGC register 43, respectively, and stores the read-out same values inthe data memory 62. Further, at step S43, with controlling thehigh-frequency signal generator 65 to change the inputted signal levelof the high-frequency signal inputted to the input terminal 1 and havingthe maximum frequency f_(2max) of 861 MHz within the second frequencyrange FR2 from −20 dBmV to +20 dBmV every one dBmV, the controller 60reads out IFAGC register values and RFAGC register values correspondingto the inputted signal levels from the IFAGC register 33 and therespective RFAGC register 43, respectively, and stores the read-out samevalues in the data memory 62. Then, at step S44, the controller 60calculates the approximate function AF31 a of the relationship of theIFAGC register values to the respective inputted signal levels at theminimum frequency f_(min) within the first frequency range FR1 based onthe data representing the relationship. At step S45, the controller 60calculates the approximate function AF31 b of the relationship of theRFAGC register values to the respective inputted signal levels at theminimum frequency f_(1min) within the first frequency range FR1 based onthe data representing the relationship. The processing flow goes to stepS46 shown in FIG. 14.

At step S46 shown in FIG. 14, the controller 60 calculates theapproximate function AF32 a=AF41 a of the relationship of the IFAGCregister values to the respective inputted signal levels at the maximumfrequency f_(1max) in the first frequency range FR1 and at the minimumfrequency f_(2min) within the second frequency range FR2 based on thedata representing the relationship. At step S47, the controller 60calculates the approximate function AF32 b=AF41 b for the relationshipof the RFAGC register values to the respective inputted signal levels atthe maximum frequency f_(1max) within the first frequency range FR1 andat the minimum frequency f_(2min) in the second frequency range FR2based on the data representing the relationship. Next, at step S48, thecontroller 60 calculates the approximate function AF42 a of therelationship of the IFAGC register values to the respective inputtedsignal levels at the maximum frequency f_(2max) within the secondfrequency range FR2 based on the data representing the relationship. Atstep S49, the controller 60 calculates the approximate function AF42 bfor the relationship of the RFAGC register values to the respectiveinputted signal levels at the maximum frequency f_(2max) within thesecond frequency range FR2 based on the data representing therelationship. Further, at step S50, the controller 60 generates adisplay control program (FIG. 15) including the calculated approximatefunctions AF31 a, AF31 b, AF32 a=AF41 a, AF32 b=AF41 b, AF42 a, and AF42b, and writes the generated display control program in the programmemory 51 of the controller 50, thus finishing the processing forgenerating the display control program.

FIG. 15 is a flowchart showing a processing for controlling display,which is executed by a controller 50 according to the third preferredembodiment.

Referring to FIG. 15, at step S51, the controller 50 judges whether ornot a command to display the inputted signal level is inputted from aninput unit 53. If YES at step S51, the processing flow goes to step S52.If NO at step S51, the processing flow returns to step S51. At step S52,the controller 50 reads out the IFAGC register value from the IFAGCregister 33 and reads out the RFAGC register value from the RFAGCregister value 43. Next, at step S53, the controller 50 judges whetheror not a current reception frequency f_(rec) is fallen within the firstfrequency range FR1. If YES at step S53, the processing flow goes tostep S54. If NO at step S53, the processing flow goes to step S56.

At step S54, the controller 50 calculates the inputted signal level Pifat the minimum frequency f_(1min) using the approximate function AF31 abased on the read-out IFAGC register value. The controller 50 calculatesthe inputted signal level Prf at the minimum frequency f_(1min) usingthe approximate function AF31 b based on the read-out RFAGC registervalue. In addition, the controller 50 calculates the average valueP_(fmin)=(Pif+Prf/2 of them. Next, at step S55, the controller 50calculates the inputted signal level Pif at the maximum frequencyf_(1max) using the approximate function AF32 a based on the read-outIFAGC register value. The controller 50 calculates the inputted signallevel Prf at the maximum frequency f_(1max) using the approximatefunction AF32 b based on the read-out RFAGC register value. In addition,the controller 50 calculates the average value P_(fmax)=(Pif+Prf/2 ofthem. Thereafter, the processing flow goes to step S58.

At step S56, the controller 50 calculates the inputted signal level Pifat the minimum frequency f_(2min) using the approximate function AF41 abased on the read-out IFAGC register value. The controller 50 calculatesthe inputted signal level Prf at the minimum frequency f_(2min) usingthe approximate function AF41 b based on the read-out RFAGC registervalue. In addition, the controller 50 calculates the average valueP_(fmin)=(Pif+Prf/2 of them. Next, at step S57, the controller 50calculates the inputted signal level Pif at the maximum frequencyf_(2max) using the approximate function AF42 a based on the read-outIFAGC register value. The controller 50 calculates the inputted signallevel Prf at the maximum frequency f_(2max) using the approximatefunction AF42 b based on the read-out RFAGC register value. In addition,the controller 50 calculates the average value P_(fmax)=(Pif+Prf)/2 ofthem. Thereafter, the processing flow goes to step S58.

Further, at step S58, the controller 50 calculates the inputted signallevel Pin using the equation (2) by the linear approximation methodbased on the calculated inputted signal levels P_(fmin) and P_(fmax). Atstep S59, the controller 50 generates display data for displaying thecalculated inputted signal level Pin, and outputs the generated displaydata to an OSD controller 19. The processing flow then returns to stepS51.

As described so far, in the processing for controlling display shown inFIG. 15 according to the third preferred embodiment, when the user viewsand listens to the digital broadcasting signal, the inputted signallevel Pif is calculated using the approximate function corresponding tothe minimum frequency within the frequency range FR1 or FR2 included inthe frequency of the viewed digital broadcasting signal based on theIFAGC register value. The inputted signal level Prf is calculated usingthe approximate function corresponding to the minimum frequency withinthe frequency range FR1 or FR2 included in the frequency of the vieweddigital broadcasting signal based on the RFAGC register value. Theaverage value of the inputted signal levels Pif and Prf is calculated asthe inputted signal level P_(fmin) of the minimum frequency. Inaddition, the inputted signal level Pif is calculated using theapproximate function corresponding to the maximum frequency within thefrequency range FR1 or FR2 included in the frequency of the vieweddigital broadcasting signal based on the IFAGC register value. Theinputted signal level Prf is calculated using the approximate functioncorresponding to the maximum frequency within the frequency range FR1 orFR2 included in the frequency of the viewed digital broadcasting signalbased on the RFAGC register value. The average value of the inputtedsignal levels Pif and Prf is calculated as the inputted signal levelP_(fmax) of the maximum frequency. Using the inputted signal levelP_(fmin) at the minimum frequency in this frequency range and theinputted signal level P_(fmax) at the maximum frequency in thisfrequency range, the inputted signal level Pin is calculated anddisplayed using the equation (2) by the linear approximation method.Therefore, it is possible to average the errors shown in FIGS. 7 and 8described above, correct the error due to a change in the frequency ofthe broadcasting signal in light of a frequency deviations from theminimum frequency and the maximum frequency, and detect and display theinputted signal level of the received broadcasting signal with accuracyhigher than that of the prior art.

Fourth Preferred Embodiment

FIG. 16 is a flowchart showing a processing for generating a displaycontrol program, which is executed by a controller 60 of a measurementcontrol system according to a fourth preferred embodiment. FIG. 17 is aflowchart showing a processing for controlling display, which isexecuted by a controller 50 according to the fourth preferredembodiment.

The fourth preferred embodiment is characterized as follows. Attentionis paid to facts, as apparent from the graph of FIG. 6, that when anRFAGC register value is the maximum value thereof (when an inputtedsignal level is smaller than a predetermined threshold value (about −6dBmV in FIG. 6)), only the IFAGC register value is generally changedrelative to the inputted signal level and that when the IFAGC registervalue is not the maximum value thereof (when the inputted signal levelexceeds the threshold value), only an RFAGC register value is generallychanged relative to the inputted signal level. In the former case, theinputted signal level is detected based on the IFAGC register value. Onthe other hand, in the latter case, the inputted signal level isdetected based on the RFAGC register value. Concretely, the maximumvalue of measured RFAGC register values is searched. A range of theinputted signal level at which the RFAGC register value is the maximumvalue thereof (where an attenuation amount of the attenuator 4 shown inFIG. 1 has the minimum value thereof and a gain for a high-frequencysignal has the maximum value thereof) is searched, and the searchedrange is set as a first level range LR1. A range of the inputted signallevel, at which the RFAGC register value does not have the maximum valuethereof, is set as a second level range LR2. In the first level rangeLR1, an inputted signal level Pin is calculated using an approximatefunction AF51 in this range LR1 based on the IFAGC register value. Onthe other hand, in the second level range LR2, the inputted signal levelPin is calculated using an approximate function AF52 in this range LR2based on the RFAGC register value.

In the processing for generating the display control program shown inFIG. 16, at step S61, with controlling a high-frequency signal generator65 to change the inputted signal level of the high-frequency signalinputted to an input terminal 1 from −20 dBmV to +20 dBmV every onedBmV, the controller 60 measures IFAGC register values and RFAGCregister values corresponding to the inputted signal levels, and storesthe measured same values in a data memory 62. Next, at step S62, thecontroller 50 searches the maximum value of the RFAGC register valuesbased on the measured RFAGC register values and stores the searchedmaximum value in the data memory 62. In addition, the controller 50searches a range of the inputted signal level when the RFAGC registervalue has the maximum value thereof, and sets the searched range as thefirst level range LR1. The controller 50 sets a range of the inputtedsignal level when the RFAGC register value does not have the maximumvalue thereof as the second level range LR2. Then, at step S63, thecontroller 60 calculates the approximate function AF51 of therelationship of the IFAGC register values to the respective inputtedsignal levels within the first level range LR1 based on the datarepresenting this relationship. At step S64, the controller 60calculates the approximate function AF52 of the relationship of theRFAGC register values to the respective inputted signal levels withinthe second level range LR2 based on the data representing thisrelationship. Further, at step S65, the controller 60 generates adisplay control program (FIG. 17) including the calculated approximatefunctions AF51 and AF52, and writes the generated display controlprogram in a program memory 51 of the controller 50, thus finishing theprocessing for generating the display control program.

In the processing for controlling display shown in FIG. 17, at step S71,the controller 50 judges whether or not a command to display theinputted signal level is inputted from an input unit 53. If YES at stepS71, the processing flow goes to step S72. If NO at step S71, theprocessing flow returns to step S71. At step S72, the controller 50reads out the IFAGC register value from an IFAGC register 33 and readsout the RFAGC register value from an RFAGC register value 43. Then, atstep S73, the controller 50 judges whether or not the read-out RFAGCregister value is the maximum value of the RFAGC register values. If YESat step S73, the processing flow goes to step S74. If NO at step S73,the processing flow goes to step S75. At step S74, the controller 50calculates the inputted signal level Pin using the approximate functionAF51 based on the read-out IFAGC register value. Thereafter, theprocessing flow goes to step S76. On the other hand, at step S75, thecontroller 50 calculates the inputted signal level Pin using theapproximate function AF52 based on the read-out RFAGC register value.Thereafter, the processing flow goes to step S76. Further, at step S76,the controller 50 generates display data for displaying the calculatedinputted signal level Pin, and outputs the generated display data to anOSD controller 19. The processing flow then returns to step S71.

FIG. 18 is a graph showing an approximate function AF52 obtained byapproximating measurement results of the relationship of the inputtedsignal level equal to or larger than a predetermined threshold value tothe RFAGC register value by using a predetermined approximate function.FIG. 19 is a graph showing an approximate function AF51 obtained byapproximating measurement results of the relationship of the inputtedsignal level equal to or smaller than the predetermined threshold valueto an IFAGC register value by using a predetermined approximatefunction. As apparent from FIGS. 18 and 19, the inputted signal levelcan be detected uniquely from the RFAGC register value and the IFAGCregister value on each of the graphs. The reason for this is as follows.When the control flow is not branched based on the condition of theinputted signal level at step S73 shown in FIG. 17, a linear functionpart (linear part) and a quadric function (curve part) are present asapparent from the graphs shown in FIGS. 7 and 8. In particular, near apart between the linear function and the quadric function, an error maybe caused between the approximate function and actual inputted signallevel. On the other hand, as described in the present preferredembodiment, the control flow may be branched based on the condition ofthe inputted signal level at step S73 shown in FIG. 17, and this leadsto that these two functions are not present simultaneously on the samegraph. Therefore, an approximate function calculation error is small.Accordingly, the accuracy for detecting the inputted signal level can beadvantageously and remarkably improved.

Fifth Preferred Embodiment

FIGS. 20 and 21 are flowcharts showing a processing for generating adisplay control program, which is executed by a controller 60 of ameasurement control system according to a fifth preferred embodiment.FIG. 22 is a flowchart showing a processing for controlling display,which is executed by a controller 50 according to the fifth preferredembodiment.

The fifth preferred embodiment is characterized by the use of thecalculation of approximate functions by dividing the frequency range ofthe broadcasting signal into the two ranges according to the secondpreferred embodiment in addition to such a use that the control flow isbranched based on the condition of the inputted signal level accordingto the fourth preferred embodiment.

In the processing for generating the display control program shown inFIG. 20, at step S81, with controlling a high-frequency signal generator65 to change the inputted signal level of a high-frequency signalinputted to an input terminal 1 and having a general central frequencyf_(1c) of 255 MHz-within a first frequency range FR1 from −20 dBmV to+20 dBmV every one dBmV, the controller 60 reads out IFAGC registervalues and RFAGC register values corresponding to the respectiveinputted signal levels from an IFAGC register 33 and an RFAGC register43, respectively, and stores the read-out same values in a data memory62. Next, at step S82, the controller 60 searches the maximum value ofthe RFAGC register values based on the measured RFAGC register valuesfor the first frequency range FR1, and stores the searched maximum valuethereof in the data memory 62. In addition, the controller 60 searches arange of the inputted signal level when the RFAGC register value has themaximum value thereof, and sets the searched range as a level range LR11of the first frequency range FR1. The controller 60 sets a range of theinputted signal level when the RFAGC register value does not have themaximum value thereof as a level range LR12 of the first frequency rangeFR1. Then, at step S83, the controller 60 calculates an approximatefunction AF61 of a relationship of the IFAGC register values to therespective inputted signal levels within the level range LR11 based onthe data representing this relationship. At step S84, the controller 60calculates an approximate function AF62 of a relationship of the RFAGCregister values to the respective inputted signal levels within thelevel range LR12 based on the data representing this relationship.Further, at step S85, with controlling the high-frequency signalgenerator 65 to change the inputted signal level of the high-frequencysignal inputted to the input terminal 1 and having a general centralfrequency f_(2c) of 255 MHz within a second frequency range FR2 from −20dBmV to +20 dBmV every one dBmV, the controller 60 reads out IFAGCregister values and RFAGC register values corresponding to therespective inputted signal levels from the IFAGC register 33 and theRFAGC register 43, respectively, and stores the read-out same values inthe data memory 62. Thereafter, the processing flow goes to step S86shown in FIG. 21.

At step S86 shown in FIG. 21, the controller 60 searches the maximumvalue of the RFAGC register values based on the measured RFAGC registervalues for the second frequency range FR2, and stores the searchedmaximum value thereof in the data memory 62. In addition, the controller60 searches a range of the inputted signal levels when the RFAGCregister value has the maximum value thereof, and sets the searchedrange as a level range LR21 of the second frequency range FR2. Thecontroller 60 sets the range of the inputted signal levels when theRFAGC register value does not have the maximum value thereof as a levelrange LR22 of the second frequency range FR2. Next, at step S87, thecontroller 60 calculates an approximate function AF71 of a relationshipof the IFAGC register values to the respective inputted signal levelswithin the level range LR21 based on the data representing thisrelationship. At step S88, the controller 60 calculates an approximatefunction AF72 of a relationship of the RFAGC register values to therespective inputted signal levels within the level range LR22 based onthe data representing this relationship. Further, at step S89, thecontroller 60 generates a display control program (FIG. 22) includingthe calculated approximate functions AF61, AF62, AF71 and AF72, andwrites the generated display control program in a program memory 51 ofthe controller 50, thus finishing the processing for generating thedisplay control program.

In the processing for controlling display shown in FIG. 22, at step S91,the controller 50 judges whether or not a command to display theinputted signal level is inputted from an input unit 53. If YES at stepS91, the processing flow goes to step S92. On the other hand, if NO atstep S91, the processing flow returns to step S91. Next, at step S92,the controller 50 reads out the IFAGC register value from an IFAGCregister 33 and reads out the RFAGC register value from an RFAGCregister value 43. At step S93, the controller 50 judges whether or nota current reception frequency is fallen within the first frequency rangeFR1. If YES at step S93, the processing flow goes to step S94. On theother hand, if NO at step S93, the processing flow goes to step S97.Then, at step S94, the controller 50 judges whether or not the read-outRFAGC register value is the maximum value of the RFAGC register values.If YES at step S94, the processing flow goes to step S95. On the otherhand, if NO at step S94, the processing flow goes to step S96. At stepS95, the controller 50 calculates an inputted signal level Pin using theapproximate function AF61 based on the read-out IFAGC register value,and the processing flow goes to step S100. On the other hand, at stepS96, the controller 50 calculates the inputted signal level Pin usingthe approximate function AF62 based on the read-out RFAGC registervalue, and the processing flow goes to step S100.

Next, at step-S97, the controller 50 judges whether or not the read-outRFAGC register value is the maximum value of the RFAGC register values.If YES at step S97, the processing flow goes to step S98. On the otherhand, if NO at step S97, the processing flow goes to step S99. At stepS98, the controller 50 calculates the inputted signal level Pin usingthe approximate function AF71 based on the read-out IFAGC registervalue, and the processing flow goes to step S100. On the other hand, atstep S99, the controller 50 calculates the inputted signal level Pinusing the approximate function AF72 based on the read-out RFAGC registervalue, and the processing flow goes to step S100. Further, at step S100,the controller 50 generates display data for displaying the calculatedinputted signal level Pin, and outputs the generated display data to anOSD controller 19. The processing flow then returns to step S91.

As stated above, according to the fifth preferred embodiment, by usingthe calculation of the approximate functions by dividing the frequencyrange of the broadcasting signal into the two ranges according to thesecond preferred embodiment in addition to such a use that the controlflow is branched based on the condition of the inputted signal levelaccording to the fourth preferred embodiment, accuracy for detecting theinputted signal level of the high-frequency signal can be moreremarkably improved.

Sixth Preferred Embodiment

FIGS. 23 and 24 are flowcharts showing a processing for generating adisplay control program, which is executed by a controller 60 of ameasurement control system according to a sixth preferred embodiment.FIG. 25 is a flowchart showing a processing for controlling display,which is executed by a controller 50 according to the sixth preferredembodiment.

The sixth preferred embodiment is characterized by detecting an inputtedsignal level based on such a condition as to whether or not the RFAGCregister value is the maximum value thereof according to the fourthpreferred embodiment in addition to such a use that the control flow isbranched based on the condition of the inputted signal level accordingto the fourth preferred embodiment as well as the use of the calculationof approximate functions by dividing the frequency range of thebroadcasting signal into the two ranges according to the secondpreferred embodiment.

In the processing for generating the display control program shown inFIG. 23, at step S101, with controlling a high-frequency signalgenerator 65 to change the inputted signal level of the high-frequencysignal inputted to an input terminal 1 and having a minimum frequencyf_(1min) of 57 MHz within a first, frequency range FR1 from −20 dBmV to+20 dBmV every one dBmV, the controller 60 reads out. IFAGC registervalues and RFAGC register values corresponding to the respectiveinputted signal levels from an IFAGC register 33 and an RFAGC register43, respectively, and stores the read-out same values in a data memory62. Next, at step S102, with controlling the high-frequency signalgenerator 65 to change the inputted signal level of the high-frequencysignal inputted to the input terminal 1 and having a maximum frequencyf_(1max) of 459 MHz within the first frequency range FR1 and a minimumfrequency f_(2min) of 459 MHz within a second frequency range FR2 from−20 dBmV to +20 dBmV every one dBmV, the controller 60 reads out IFAGCregister values and RFAGC register values corresponding to therespective inputted signal levels from the IFAGC register 33 and theRFAGC register 43, respectively, and stores the read-out same values inthe data memory 62. Further, at step S103, with controlling thehigh-frequency signal generator 65 to change the inputted signal levelof the high-frequency signal inputted to the input terminal 1 and havinga maximum frequency f_(2max) of 861 MHz within the second frequencyrange FR2 from −20 dBmV to +20 dBmV every one dBmV, the controller 60reads out IFAGC register values and RFAGC register values correspondingto the respective inputted signal levels from the IFAGC register 33 andthe RFAGC register 43, respectively, and stores the read-out same valuesin the data memory 62.

At step S104, the controller 60 searches the maximum value of the RFAGCregister values based on the measured RFAGC register values at theminimum frequency f_(1min) of the first frequency range FR1, and storesthe searched maximum value thereof in the data memory 62 as the maximumvalue of the RFAGC register values within the first frequency range FR1.In addition, the controller 60 searches a range of the inputted signallevels when the RFAGC register value has the maximum value thereof, andsets the searched range as a level range LR11 of the first frequencyrange FR1. The controller 60 sets the range of the inputted signal levelwhen the RFAGC register value does not have the maximum value thereof asa level range LR12 of the first frequency range FR1. Next, at step S105,the controller 60 searches the maximum value of the RFAGC registervalues based on the measured RFAGC register values at the minimumfrequency f_(2min) in the second frequency range FR2, and stores thesearched maximum values thereof within the data memory 62 as the maximumvalue of the RFAGC register values in the second frequency range FR2. Inaddition, the controller 60 searches a range of the inputted signallevels when the RFAGC register value has the maximum value thereof, andsets the searched range as a level range LR21 of the second frequencyrange FR2. The controller 60 sets the range of the inputted signallevels when the RFAGC register value does not have the maximum valuethereof as a level range LR22 of the second frequency range FR2.

At step S106 shown in FIG. 24, the controller 60 calculates anapproximate function AF81 a of a relationship of the IFAGC registervalues to the respective inputted signal levels within the level rangeLR11 at the minimum frequency f_(1min) within the first frequency rangeFR1 based on the data representing this relationship. At step S107, thecontroller 60 calculates an approximate function AF81 b of arelationship of the RFAGC register values to the respective inputtedsignal levels within the level range LR12 at the minimum frequencyf_(1min) within the first frequency range FR1 based on the datarepresenting this relationship. Next, at step S108, the controller 60calculates an approximate function AF82 a=AF91 a of a relationship ofthe IFAGC register values to the respective inputted signal levelswithin the level range LR21 at the maximum frequency f_(1max) within thefirst frequency range FR1 and at the minimum frequency f_(2min) in thesecond frequency range FR2 based on the data representing thisrelationship. At step S109, the controller 60 calculates an approximatefunction AF82 b=AF91 b of a relationship of the RFAGC register values tothe respective inputted signal levels within the level range LR22 at themaximum frequency f_(1max) within the first frequency range FR1 and atthe minimum frequency f_(2min) within the second frequency range FR2based on the data representing this relationship. Further, at step S110,the controller 60 calculates an approximate function AF92 a of arelationship of the IFAGC register values to the respective inputtedsignal levels within the level range LR21 at the maximum frequencyf_(2max) within the second frequency range FR2 based on the datarepresenting this relationship. At step S111, the controller 60calculates an approximate function AF92 b of a relationship of the RFAGCregister values to the respective inputted signal levels within thelevel range LR22 at the maximum frequency f_(2max) within the secondfrequency range FR2 based on the data representing this relationship.Furthermore, at step S112, the controller 60 generates a display controlprogram (FIG. 25) including the calculated approximate functions AF81 a,AF81 b, AF82 a=AF91 a, AF82 b=AF91 b, AF92 a, and AF92 b, and writes thegenerated display control program in a program memory 51 of thecontroller 50, thus finishing the processing for generating the displaycontrol program.

In the processing for controlling display shown in FIG. 25, at stepS121, the controller 50 judges whether or not a command to display theinputted signal level is inputted from an input unit 53. If YES at stepS121, the processing flow goes to step S122. On the other hand, if NO atstep S121, the processing flow returns to step S121. At step S122, thecontroller 50 reads out the IFAGC register value from an IFAGC register33 and reads out the RFAGC register value from an RFAGC register value43. At step S123, the controller 50 judges whether or not a currentreception frequency f_(rec) is fallen within the first frequency rangeFR1. If YES at step S123, the processing flow goes to step S124. On theother hand, if NO at step S123, the processing flow goes to step S127.

Next, at step S124, the controller 50 judges whether or not the read-outRFAGC register value is the maximum value of the RFAGC register values.If YES at step S124, the processing flow goes to step S125. On the otherhand, if NO at step S124, the processing flow goes to step S126. At stepS125, the controller 50 calculates an inputted signal level P_(fmin) atthe minimum frequency f_(1min) using the approximate function AF81 a andan inputted signal level P_(fmax) at the maximum frequency f_(1max)using the approximate function AF82 a based on the read-out IFAGCregister value, and the processing flow goes to step S130. On the otherhand, at step S126, the controller 50 calculates an inputted signallevel P_(fmin) at the minimum frequency f_(1min) using the approximatefunction AF81 b and an inputted signal level P_(fmax) at the maximumfrequency f_(1max) using the approximate function AF82 b based on theread-out RFAGC register value, and the processing flow goes to stepS130.

Next, at step S127, the controller 50 judges whether or not the read-outRFAGC register value is the maximum value of the RFAGC register values.If YES at step S127, the processing flow goes to step S128. On the otherhand, if NO at step S127, the processing flow goes to step S129. At stepS128, the controller 50 calculates the inputted signal level P_(fmin) atthe minimum frequency f_(1min) using the approximate function AF91 a andthe inputted signal level P_(fmax) at the maximum frequency f_(1max)using the approximate function AF92 a based on the read-out IFAGCregister value, and the processing flow goes to step S130. On the otherhand, at step S129, the controller 50 calculates the inputted signallevel P_(fmin) at the minimum frequency f_(1min) using the approximatefunction AF91 b and the inputted signal level P_(fmax) at the maximumfrequency f_(1max) using the approximate function AF92 b based on theread-out RFAGC register value, and the processing flow goes to stepS130.

Further, at step S130, the controller 50 calculates an inputted signallevel Pin using the equation (2) by the linear approximation methodbased on the calculated inputted signal levels P_(fmin) and P_(fmax). Atstep S131, the controller 50 generates display data for displaying thecalculated inputted signal level Pin, and outputs the generated displaydata to an OSD controller 19, thus finishing the processing forcontrolling display.

As stated above, according to the sixth preferred embodiment, theinputted signal level is detected based on condition as to whether ornot the RFAGC register value is the maximum value thereof according tothe fourth preferred embodiment in addition to such a use that thecontrol flow is branched based on the inputted signal level according tothe condition according to the fourth preferred embodiment as well asthe use of the calculation of approximate functions by dividing thefrequency range of the broadcasting signal into the two ranges accordingto the second preferred embodiment. Therefore, the accuracy fordetecting the inputted signal level of the high-frequency signal can befurther improved.

Seventh Preferred Embodiment

FIG. 26 is a spectral view showing such a case that two interferencesignals on adjacent channels are present in the vicinity and on bothsides of a reception channel for a television receiver 100 according toa seventh preferred embodiment. As shown in FIG. 26, when a spectralenergy of a broadcasting signal on the adjacent channel is present oneach or one side of the reception channel on which an inputted signallevel is detected, there is caused such a problem that one or twointerference signals due to a broadcasting signal on each adjacentchannel causes a detected error in detection of the inputted signallevel of the broadcasting signal. The reason for this is as follows. Anintermediate frequency signal processing circuit such as the bandpassfilter 8 shown in FIG. 1 does not exhibit a sharp bandpass filteringcharacteristic that the circuit can completely remove the interferencesignal on the adjacent channel.

FIG. 27 is a graph showing IFAGC register values and RFAGC registervalues relative to inputted signal levels in three cases when theinterference signal on adjacent channel is not present, when oneinterference signal is present, and when two interference signals arepresent, respectively, in the television receiver 100 according to theseventh preferred embodiment. As apparent from FIG. 27, display errorsmay be caused to the RFAGC register values and the IFAGC register valuesrelative to the respective inputted signal levels. Concretely, as forthe IFAGC register value, a detected error ER1 is caused when oneinterference signal is present as compared with such a case that nointerference signal is present, and a detected error ER2 (>ER1) iscaused when two interference signals are present as compared with such acase that no interference signal is present. It is also seen from FIG.27 that the detected error due to the interference signal is greaterwhen the inputted signal level is almost equal to or larger than about−10 dBmV (in other words, when the RFAGC register value is not themaximum value thereof).

In other words, FIG. 27 exemplarily shows the above-stated three cases.For an actually distributed broadcasting signal, various kinds ofpatterns of a relationship of a DU ratio of a broadcasting signal on areception channel to a broadcasting signal on an adjacent channel arepresent. Therefore, according to the present preferred embodiment, sucha case that the reception channel is located at an intermediate positionin a channel allocation and that adjacent channels (two interferencesignals) are present on both sides of the reception channel,respectively, and such a case that the reception channel is located atan end in the channel allocation and that an adjacent channel (oneinterference signal) is present only on one side of the receptionchannel are considered. An approximate function AF102 of the detectederror ER2 in the former case and an approximate function AF101 for thedetected error ER1 in the latter case are measured in advance. Inaddition, when the RFAGC register value is not the maximum valuethereof, a detection level of the inputted signal level of the receivedbroadcasting signal is corrected using the detected error ER1 or ER2calculated using the approximate function AF101 or AF102 based on theIFAGC register value, whose change amount is larger than that of theRFAGC register value.

FIG. 28 is a graph showing the IFAGC register value relative to a ratio(U/D) of an interference signal power to a desired wave power in thetelevision receiver 100 according to the seventh preferred embodiment.As apparent from FIG. 28, as the ratio (U/D) of the interference signalpower to the desired wave power becomes greater, the IFAGC registervalue also increases.

FIG. 29 is a graph showing a display error ER2 of the inputted signallevel relative to the IFAGC register value in the television receiver100 according to the seventh preferred embodiment. In the example ofFIG. 29, the approximate function AF102 when two interference signalsare present is shown. Likewise, the approximate function AF101 when oneinterference signal is present is calculated in advance. The presentpreferred embodiment is characterized as follows. By executing aprocessing for correcting the detected error shown in FIG. 30 usingthese two approximate functions AF101 and AF102, the detected error inthe inputted signal level can be corrected based on the IFAGC registervalue, in particular when the IFAGC register value is not the maximumvalue thereof and the detected error is relatively large.

FIG. 30 is a flowchart that showing a characteristic part of aprocessing for controlling display, which is executed by a controller 50according to the seventh preferred embodiment. The characteristic partof this processing relates to the processing for correcting the detectederror, and is inserted between steps S130 and S131 shown in FIG. 25.

After the processing at step S130 shown in FIG. 25, the processing flowgoes to step S141 shown in FIG. 30. At step S141, the controller 50judges whether or not the read-out RFAGC register value is the maximumvalue of the RFAGC values. If YES at step S141, the processing flow goesto step S131 shown in FIG. 25. On the other hand, if NO at step S141,the processing flow goes to step S142. At step S142, the controller 50judges whether or not adjacent channels are present on the both sides ofthe reception channel. If YES at step S142, the controller 50 judgesthat two interference signals are present and the processing flow goesto step S143. On the other hand, if NO at step S142, the controller 50judges that one interference signal is present and the processing flowgoes to step S145. At step S143, the controller 50 calculates thedetected error ER2 using the approximate function AF102 of the detectederror of the inputted signal level based on the read-out IFAGC registervalue. At step S144, the controller 50 sets the detected error ER2 as adetected error ER, and the processing flow goes to step S147. On theother hand, at step S145, the controller 50 calculates the detectederror ER1 using the approximate function AF101 of the detected error inthe inputted signal level based on the read-out IFAGC register value. Atstep S144, the controller 50 sets the detected error ER1 as the detectederror ER, and the processing flow goes to step S147. Further, at stepS147, the controller 50 adds the detected error ER to the previouslycalculated inputted signal level Pin, and sets an addition result as theinputted signal level Pin. Thereafter, the processing flow goes to stepS131 shown in FIG. 25.

As stated above, according to the seventh preferred embodiment, theprocessing for correcting the detected error shown in FIG. 30 isexecuted using the two approximate functions AF101 and AF102 calculatedin advance, and this leads to that the detected error in the inputtedsignal level is corrected based on the IFAGC register value, inparticular when the IFAGC register is not the maximum value thereof andthe detected error is relatively large. Then it is possible toremarkably improve the detected error in the inputted signal level ofthe broadcasting signal.

In the seventh preferred embodiment stated above, the control flow isbranched into such a case of one interference signal and such anothercase of two interference signals at step S142. However, the latter caseapplies to most cases. Therefore, only the processing in the latter casemay be executed. Further, an average value of the detected errors inthese two cases may be used as the detected error and the inputtedsignal level may be corrected using this detected error.

The processing for correcting the detected error according to theseventh preferred embodiment stated above is inserted between steps S130and S131 shown in FIG. 25. However, the present invention is not limitedto this. The processing for correcting the detected error according tothe present preferred embodiment may be executed for the detected valueof the inputted signal level Pin in any of the first to fifth preferredembodiments stated above.

MODIFICATION EXAMPLES

In the preferred embodiments stated so far, the attenuation amount ofthe attenuator 4 is changed so as to control the gain for thehigh-frequency signal in the television receiver 100 shown in FIG. 1.However, the preset invention is not limited to this. The amplificationfactor of the high-frequency amplifier 3 may be changed.

In the preferred embodiments stated so far, the amplification factor ofthe intermediate frequency amplifier 7 is changed so as to control thegain for the intermediate frequency signal in the television receiver100 shown in FIG. 1. However, the present invention is not limited tothis. The amplification ratio of the other intermediate frequencyamplifier 9 or the attenuation amount of the attenuator inserted whilethe frequency is the intermediate frequency may be changed.

In the preferred embodiments stated so far, the television receiver 100shown in FIG. 1 has been described. However, the present invention isnot limited to this. A part of a set-top box that includes a function ofdetecting the inputted signal level may be separately provided. Further,a high-frequency signal level detection apparatus or a high-frequencysignal receiver apparatus that include a function of detecting aninputted signal level of a high-frequency signal other than thebroadcasting signal may be provided.

In the preferred embodiments stated so far, the processings performed bythe characteristic parts according to the respective preferredembodiments and combinations thereof have been described. However, thepresent invention is not limited to this and processings in combinationsother than the above-stated combinations may be executed.

INDUSTRIAL APPLICABILITY

As stated so far, according to the present invention, the firstrelational data indicating the RFAGC value relative to the inputtedsignal level of the received high-frequency signal and the secondrelational data indicating the IFAGC value relative to the inputtedsignal level of the received high-frequency signal are measured inadvance. The RFAGC value and the IFAGC value when the high-frequencysignal to be measured is received are measured. Based on the measuredRFAGC value and IFAGC value, the inputted signal level of the receivedhigh-frequency signal is detected using the measured first and secondrelational data. Therefore, it is possible to provide the high-frequencysignal level detection apparatus capable of detecting the signal levelof the high-frequency signal with accuracy higher than that of the priorart, and the high-frequency signal receiver apparatus using the same. Inthis case, the high-frequency signal level detection apparatus accordingto the present invention can be applied to, for example, ahigh-frequency signal receiver apparatus such as a set-top box or atelevision receiver that receives a radio broadcasting signal inaddition to a CATV set-top box or a CATV television receiver.

1. A high-frequency signal level determining apparatus comprising: anAGC circuit for executing an automatic gain control on an intermediatefrequency signal obtained by converting a frequency of a receivedhigh-frequency signal, using an RFAGC value for controlling a gain ofthe received high-frequency signal and an IFAGC value for controlling again of the intermediate frequency signal based on the intermediatefrequency signal so that an output level of the intermediate frequencysignal is substantially constant; and determining means for previouslymeasuring first relational data indicating an RFAGC value relative to aninputted signal level of a generated high-frequency signal and secondrelational data indicating an IFAGC value relative to the inputtedsignal level of the generated high-frequency signal, for measuring theRFAGC value and the IFAGC value when a high-frequency signal to bemeasured is received, and for determining the inputted signal level ofthe received high-frequency signal using the measured first and secondrelational data based on the measured RFAGC value and IFAGC value,wherein the received high-frequency signal has a plurality offrequencies, and wherein said determining means previously measures afirst relational data indicating the RFAGC value relative to theinputted signal level and a second relational data indicating the IFAGCvalue relative to the inputted signal level, using a generatedhigh-frequency signal having a substantial central frequency among theplurality of frequencies.
 2. The high-frequency signal level determiningapparatus as claimed in claim 1, wherein said determining meansdetermines the inputted signal level of the received high-frequencysignal using only the second relational data based on the measured IFAGCvalue when the gain of the received high-frequency signal is a maximumvalue thereof.
 3. The high-frequency signal level determining apparatusas claimed in claim 1, wherein said determining means determines theinputted signal level of the received high-frequency signal using onlythe first relational data based on the measured RFAGC value when thegain of the received high-frequency signal is not a maximum valuethereof.
 4. The high-frequency signal level determining apparatus asclaimed in claim 1, wherein said determining means determines a firstinputted signal level of the received high-frequency signal using themeasured first relational data based on the measured RFAGC value,determined a second inputted signal level of the received high-frequencysignal using the measured second relational data based on the measuredIFAGC value, and determines an average value of the determines first andsecond inputted signal levels as the inputted signal level of thereceived high-frequency signal.
 5. The high-frequency signal leveldetermining apparatus as claimed in claim 1, wherein the receivedhigh-frequency signal has a plurality of frequencies, wherein saiddetermining means previously measures the following parts using twogenerated high-frequency signals having a maximum frequency and aminimum frequency among the plurality of frequencies, respectively: (a)a first part of the first relational data indicating the RFAGC valuerelative to the inputted signal level of the generated high-frequencysignal having the maximum frequency; (b) a first part of the secondrelational data indicating the IFAGC value relative to the inputtedsignal level of the generated high-frequency signal having the maximumfrequency; (c) a second part of the first relational data indicating theRFAGC value relative to the inputted signal level of the generatedhigh-frequency signal having the minimum frequency; and (d) a secondpart of the second relational data indicating the IFAGC value relativeto the inputted signal level of the generated high-frequency signalhaving the minimum frequency, wherein said determining means determinesa first inputted signal level of the received high-frequency signalusing the measured first part of the first relational data based on themeasured RFAGC value, determines a second inputted signal level of thereceived high-frequency signal using the measured first part of thesecond relational data based on the measured IFAGC value, and determinesan average value of the determined first and second inputted signallevels as the inputted signal level of the received high-frequencysignal having the maximum frequency, wherein said determining meansdetermines a third inputted signal level of the received high-frequencysignal using the measured second part of the first relational data basedon the measured RFAGC value, determines a fourth inputted signal levelof the received high-frequency signal using the measured second part ofthe second relational data based on the measured IFAGC value, anddetermines an average value of the determined third inputted signallevel and the determined fourth inputted signal level as the inputtedsignal level of the received high-frequency signal having the minimumfrequency, and wherein said determining means calculates the inputtedsignal level of the received high-frequency signal to be measured usinga linear approximation method for linearly approximating the inputtedsignal level relative to a reception frequency of the receivedhigh-frequency signal to be measured based on the determined inputtedsignal level of the received high-frequency signal having the maximumfrequency and on the determined inputted signal level of the receivedhigh-frequency signal having the minimum frequency.
 6. Thehigh-frequency signal level determining apparatus as claimed in claim 1,wherein the received high-frequency signal has a plurality offrequencies, wherein a frequency range including the plurality offrequencies is divided into a plurality of frequency ranges, and whereinsaid determining means previously measures the first and secondrelational data in each of the divided frequency ranges, and determinesthe inputted signal level of the received high-frequency signal usingthe measured first and second relational data corresponding to thefrequency range to which the frequency of the received high-frequencysignal to be measured belongs.
 7. The high-frequency signal leveldetermining apparatus as claimed in claim 1, wherein said determiningmeans previously measures third relational data, that is a determinederror in the IFAGC value of the second relational data indicating theIFAGC value relative to the inputted signal level of the receivedhigh-frequency signal, the determined error being caused, between a casewith an interference signal of a further received high-frequency signalin the vicinity of the frequency of the received high-frequency signalto be measured, and a case with no interference signal thereof, andwherein said determining means determines the determined error using thethird relational data based on the IFAGC value measured for the receivedhigh-frequency signal to be measured, and corrects the determinedinputted signal level using the determined error.
 8. The high-frequencysignal level determining apparatus as claimed in claim 1, wherein saiddetermining means previously measures the following parts: (a) a firstpart of third relational data, that is a first determined error in theIFAGC value of the second relational data indicating the IFAGC valuerelative to the inputted signal level of the received high-frequencysignal, the first determined error being caused, between a first casewith interference signals of further received high-frequency signalslocated on both sides of the frequency of the received high-frequencysignal to be measured, and a case with no interference signal thereof;and (b) a second part of the third relational data, that is a seconddetermined error in the IFAGC value of the second relational dataindicating the IFAGC value relative to the inputted signal level of thereceived high-frequency signal, the second determined error beingcaused, between a second case with an interference signal of furtherreceived high-frequency signal located on one side of the frequency ofthe received frequency signal to be measured, and a case with nointerference signal thereof, wherein said determining means determinesone of the first and second determined errors based on the IFAGC valuemeasured for the received high-frequency signal to be measured using oneof the first and second parts of the third relational data whichrespectively correspond to states in which the received high-frequencysignal to be measured is in the first and second cases, and corrects thedetermined inputted signal level using the determined error.
 9. Thehigh-frequency signal level determining apparatus as claimed in claim 1,wherein said determining means represents the first relational data andthe second relational data by predetermined approximate functions,respectively, and determines the inputted signal level of the receivedhigh-frequency signal using the approximate function of the firstrelational data and the approximate function of the second relationaldata.
 10. The high-frequency signal level determining apparatus asclaimed in claim 1, further comprising display means for displaying theinputted signal level determined by said determining means.
 11. Ahigh-frequency signal receiver apparatus, comprising: a receiver forreceiving a high-frequency signal, for converting the receivedhigh-frequency signal into an intermediate frequency signal, and foroutputting the intermediate frequency signal; and a high-frequencysignal level determining apparatus comprising: an AGC circuit forexecuting an automatic gain control on the intermediate frequencysignal, using an RFAGC value for controlling a gain of the receivedhigh-frequency signal and an IFAGC value for controlling a gain of theintermediate frequency signal based on the intermediate frequency signalso that an output level of the intermediate frequency signal issubstantially constant; and determining means for previously measuringfirst relational data indicating an RFAGC value relative to an inputtedsignal level of the received high-frequency signal and second relationaldata indicating an IFAGC value relative to the inputted signal level ofthe received high-frequency signal, for measuring the RFAGC value andthe IFAGC value when a high-frequency signal to be measured is received,and for determining the inputted signal level of the receivedhigh-frequency signal using the measured first and second relationaldata based on the measured RFAGC value and IFAGC value, wherein thereceived high-frequency signal has a plurality of frequencies, andwherein said determining means previously measures a first relationaldata indicating the RFAGC value relative to the inputted signal leveland a second relational data indicating the IFAGC value relative to theinputted signal levels using a generated high-frequency signal having asubstantial central frequency among the plurality of frequencies. 12.The high-frequency signal receiver apparatus as claimed in claim 11,wherein said determining means determines the inputted signal level ofthe received high-frequency signal using only the second relational databased on the measured IFAGC value when the gain of the receivedhigh-frequency signal is a maximum value thereof.
 13. The high-frequencysignal receiver apparatus as claimed in claim 11, wherein saiddetermining means determines the inputted signal level of the receivedhigh-frequency signal using only the first relational data based on themeasured RFAGC value when the gain of the received high-frequency signalis not a maximum value thereof.
 14. The high-frequency signal receiverapparatus as claimed in claim 11, wherein said determining meansdetermines a first inputted signal level of the received high-frequencysignal using the measured first relational data based on the measuredRFAGC value, determines a second inputted signal level of the receivedhigh-frequency signal using the measured second relational data based onthe measured IFAGC value, and determines an average value of thedetermined first and second inputted signal levels as the inputtedsignal level of the received high-frequency signal.
 15. Thehigh-frequency signal receiver apparatus as claimed in claim 11, whereinthe received high-frequency signal has a plurality of frequencies,wherein said determining means previously measures the following partsusing two generated high-frequency signals having a maximum frequencyand a minimum frequency among the plurality of frequencies,respectively: (a) a first part of the first relational data indicatingthe RFAGC value relative to the inputted signal level of the generatedhigh-frequency signal having the maximum frequency; (b) a first part ofthe second relational data indicating the IFAGC value relative to theinputted signal level of the generated high-frequency signal having themaximum frequency; (c) a second part of the first relational dataindicating the RFAGC value relative to the inputted signal level of thegenerated high-frequency signal having the minimum frequency; and (d) asecond part of the second relational data indicating the IFAGC valuerelative to the inputted signal level of the generated high-frequencysignal having the minimum frequency, wherein said determining meansdetermines a first inputted signal level of the received high-frequencysignal using the measured first part of the first relational data basedon the measured RFAGC value, determines a second inputted signal levelof the received high-frequency signal using the measured first part ofthe second relational data based on the measured IFAGC value, anddetermines an average value of the determined first and second inputtedsignal levels as the inputted signal level of the receivedhigh-frequency signal having the maximum frequency, wherein saiddetermining means determines a third inputted signal level of thereceived high-frequency signal using the measured second part of thefirst relational data based on the measured RFAGC value, determines afourth inputted signal level of the received high-frequency signal usingthe measured second part of the second relational data based on themeasured IFAGC value, and determines an average value of the determinedthird inputted signal level and the determined fourth inputted signallevel as the inputted signal level of the received high-frequency signalhaving the minimum frequency, and wherein said determining meanscalculates the inputted signal level of the received high-frequencysignal to be measured using a linear approximation method for linearlyapproximating the inputted signal level relative to a receptionfrequency of the received high-frequency signal to be measured based onthe determined inputted signal level of the received high-frequencysignal having the maximum frequency and on the determined inputtedsignal level of the received high-frequency signal having the minimumfrequency.
 16. The high-frequency signal receiver apparatus as claimedin claim 11, wherein the received high-frequency signal has a pluralityof frequencies, wherein a frequency range including the plurality offrequencies is divided into a plurality of frequency ranges, and whereinsaid determining means previously measures the first and secondrelational data in each of the divided frequency ranges, and determinesthe inputted signal level of the received high-frequency signal usingthe measured first and second relational data corresponding to thefrequency range to which the frequency of the received high-frequencysignal to be measured belongs.
 17. The high-frequency signal receiverapparatus as claimed in claim 11, wherein said determining meanspreviously measures third relational data, that is a determined error inthe IFAGC value of the second relational data indicating the IFAGC valuerelative to the inputted signal level of the received high-frequencysignal, the determined error being caused, between a case with aninterference signal of a further received high-frequency signal in thevicinity of the frequency of the received high-frequency signal to bemeasured, and a case with no interference signal thereof; and whereinsaid determining means determines the determined error using the thirdrelational data based on the IFAGC value measured for the receivedhigh-frequency signal to be measured, and corrects the determinedinputted signal level using the determined error.
 18. The high-frequencysignal receiver apparatus as claimed in claim 11, wherein saiddetermining means previously measures the following parts: (a) a firstpart of third relational data, that is a first determined error in theIFAGC value of the second relational data indicating the IFAGC valuerelative to the inputted signal level of the received high-frequencysignal, the first determined error being caused, between a first casewith interference signals of further received high-frequency signalslocated on both sides of the frequency of the received high-frequencysignal to be measured, and a case with no interference signal thereof,and (b) a second part of the third relational data, that is a seconddetermined error in the IFAGC value of the second relational dataindicating the IFAGC value relative to the inputted signal level of thereceived high-frequency signal, the second determined error beingcaused, between a second case with an interference signal of furtherreceived high-frequency signal located on one side of the frequency ofthe received high-frequency signal to be measured, and a case with nointerference signal thereof, wherein said determining means determinesone of the first and second determined errors based on the IFAGC valuemeasured for the received high-frequency signal to be measured using oneof the first and second parts of the third relational data whichrespectively correspond to states in which the received high-frequencysignal to be measured is in the first and second cases, and corrects thedetermined inputted signal level using the determined error.
 19. Thehigh-frequency signal receiver apparatus as claimed in claim 11, whereinsaid determining means represents the first relational data and thesecond relational data by predetermined approximate functions,respectively, and determines the inputted signal level of the receivedhigh-frequency signal using the approximate function of the firstrelational data and the approximate function of the second relationaldata.
 20. The high-frequency signal receiver apparatus as claimed inclaim 11, further comprising display means for displaying the inputtedsignal level determined by said determining means.